In office-type chairs in which the chair back is tiltable relative to the seat, control mechanisms are utilized to control the rate at which the chair back can be tilted relative to the seat. Torsion bars are commonly utilized in the chair controls to yieldably resist such tilting movement and thus control the rate of tilt. In the past, it has been the practice to mount the torsion bars in horizontal positions in which they extend from side to side with respect to the chair seat. In many cases, it has been necessary to form the torsion bar of a noncircular shape in cross section, such as rectangular, because this shape facilitates mounting of the torsion bar so that it will not be inadvertently rotated.
The prior art devices have been deficient in that they take up substantial vertical space in the chair and thus detract from the chair appearance in profile, they strengthen the chair against side to side movement but do not strengthen the chair in a front to rear direction where the principal load is placed on the chair, they present complicated bearing problems, and inherently make inefficient use of the material from which the chair control mechanism is formed, usually steel. In the case of side to side torsion bars, the torsion bar commonly performs the additional function of an axle which increases the bearing problems.
It is an object of the present invention, therefore, to provide an improved chair control mechanism which is attachable to various types of chairs and utilizes a front to rear torsion bar that can be formed from a round bar.